title: Wide-field interferometric phase microscopy with molecular specificity using plasmonic nanoparticles.
abstract: We present a method for adding molecular specificity to wide-field interferometric phase microscopy (IPM) by recording the phase signatures of gold nanoparticles (AuNPs) labeling targets of interest in biological cells. The AuNPs are excited by time-modulated light at a wavelength corresponding to their absorption spectral peak, evoking a photothermal (PT) effect due to their plasmonic resonance. This effect induces a local temperature rise, resulting in local refractive index and phase changes that can be detected optically. Using a wide-field interferometric phase microscope, we acquired an image sequence of the AuNP sample phase profile without requiring lateral scanning, and analyzed the time-dependent profile of the entire field of view using a Fourier analysis, creating a map of the locations of AuNPs in the sample. The system can image a wide-field PT phase signal from a cluster containing down to 16 isolated AuNPs. AuNPs are then conjugated to epidermal growth factor receptor (EGFR) antibodies and inserted to an EGFR-overexpressing cancer cell culture, which is imaged using IPM and verified by confocal microscopy. To the best of our knowledge, this is the first time wide-field interferometric PT imaging is performed at the subcellular level without the need for total internal reflection effects or scanning.
authors.forename: Nir A
authors.initials: NA
authors.lastname: Turko
authors.forename: Anna
authors.initials: A
authors.lastname: Peled
authors.forename: Natan T
authors.initials: NT
authors.lastname: Shaked
mesh_terms: D045744:Cell Line, Tumor; D003584:Cytological Techniques; D006046:Gold / Q000737:chemistry*; D006696:Holography; D006801:Humans; D007091:Image Processing, Computer-Assisted / Q000379:methods*; D007368:Interferometry / Q000379:methods*; D053768:Metal Nanoparticles / Q000737:chemistry*; D008858:Microscopy, Phase-Contrast / Q000379:methods*; D012815:Signal Processing, Computer-Assisted; D013817:Thermography
chemical_list: D006046:Gold